IngentaConnect Actin depolymerizing factor is essential for viability in plants,...

Authors: Augustine, Robert C.¹; Vidali, Luis¹; Kleinman, Ken P.²; Bezanilla, Magdalena

Source: The Plant Journal, Volume 54, Number 5, June 2008 , pp. 863-875(13)

Abstract:

Summary

Actin depolymerizing factor (ADF)/cofilin is important for regulating actin dynamics, and in plants is thought to be required for tip growth. However, the degree to which ADF is necessary has been elusive because of the presence of multiple ADF isoforms in many plant species. In the moss Physcomitrella patens, ADF is encoded by a single, intronless gene. We used RNA interference to demonstrate that ADF is essential for plant viability. Loss of ADF dramatically alters the organization of the F-actin cytoskeleton, and leads to an inhibition of tip growth. We show that ADF is subject to phosphorylation in vivo, and using complementation studies we show that mutations of the predicted phosphorylation site partially rescue plant viability, but with differential affects on tip growth. Specifically, the unphosphorylatable ADF S6A mutant generates small polarized plants with normal F-actin organization, whereas the phosphomimetic S6D mutant generates small, unpolarized plants with a disorganized F-actin cyotskeleton. These data indicate that phosphoregulation at serine 6 is required for full ADF function in vivo, and, in particular, that the interaction between ADF and actin is important for tip growth.

Keywords: ADF; cofilin; tip growth; phosphorylation; Physcomitrella patens

Document Type: Research article

DOI: 10.1111/j.1365-313X.2008.03451.x

Affiliations: 1: Biology Department, University of Massachusetts, Amherst, 611 North Pleasant Street, University of Massachusetts, Amherst, MA 01003-9297, USA 2: Department of Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, 133 Brookline Avenue, 6th Floor, Boston, MA 02215, USA

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Actin depolymerizing factor is essential for viability in plants, and its phosphoregulation is important for tip growth